1. Field of the Invention
The present invention relates to production of a food material having a high concentration of eriocitrin that is an antioxidant ingredient derived from citrus fruits, and use thereof. The invention is to produce a food material having a high concentration of eriocitrin from a flesh, a juice, a peel or a squeezed residue of lemon or lime having a high concentration of eriocitrin, an antioxidant ingredient of citrus fruits, and to use the same as a beverage or a food having a high antioxidant effect by adding the same to a beverage or a food.
Especially, a peel and a squeezed residue which can be used in the invention are secondary products given when squeezing a fruit juice, and the peel after having been squeezed is a portion which is discharged and mostly discarded along with a large amount of water. The extraction of an active ingredient by reusing this portion is industrially quite an effective invention, and this is extremely useful from the standpoint of reuse of a waste.
2. Description of the Related Art
Eriocitrin has a structural name, eriodictyol-7-rutinoside, and it is a flavonoid glycoside in which rutinose (disaccharide: glucose and rhamnose) is bound to eriodictyol belonging to a flavanone of flavonoid compounds. Eriocitrin is present in citrus fruits, and especially contained in lemon and lime in a large amount. It is also present in oranges. However, it has been totally unknown that eriocitrin has an excellent antioxidant property. This is a new knowledge that the present inventors found before for the first time. A novel invention on an antioxidant material derived from citrus fruits based on this new knowledge was already filed as Japanese Patent Application No. 7-218286 (JP-A-9-48969).
In Japanese Patent Application No. 7-218286 (JP-A-9-48969) of the present applicant, for producing eriocitrin, a citrus fruit is first extracted with water, an organic solvent or a mixture thereof. The extraction is conducted at from room temperature to elevated temperature. Then, the extract is concentrated (under reduced pressure), treated with a resin, and purified through high-performance liquid chromatography or another chromatography. An active fraction is collected, and dried through freeze-drying to obtain a purified powder of eriocitrin. This method is acceptable at a laboratory level, but the purification step is intricate and time-consuming. The resulting eriocitrin powder is quite expensive. Accordingly, when eriocitrin obtained by this method is used as drink and food, the drink and food are naturally expensive. In case of the drink and food, the high cost of the product is undesirable, and the low cost thereof is required. In this respect, the conventional technique is still unsatisfactory.
The invention aims to industrially produce a less costly food material having a high concentration of eriocitrin.
It has been found that in the step of removing an unnecessary peel along with feeding water after squeezing a juice of lemon or lime, the feeding water has a high concentration of eriocitrin. On the basis of this finding, researches have been assiduously conducted investigations to solve the problems, and a process for obtaining a food material having a high concentration of eriocitrin has been worked out upon focusing on the facts that eriocitrin is present in a peel in a large amount and that eriocitrin has quite a high water solubility.
When the production is conducted using feeding water of the peel as stated above, a material having a high concentration of eriocitrin can be obtained by concentrating this feeding water, namely, the water extract of the peel. However, since the resulting product has quite bitter and rough tastes, it cannot be used in a wide variety of beverages and foods as a food material.
In order to remove the bitter and rough tastes, the water extract was subjected to treatment with a synthetic adsorption resin. Then, eriocitrin was also adsorbed thereon. This treatment is not problematic when it aims to remove the bitter and rough tastes as in the conventional technique. However, a new technical problem cannot be achieved that a food material having a high concentration of eriocitrin and free from bitter and rough tastes is obtained as in the invention. Even when a synthetic adsorption resin is treated with an organic solvent, adsorption substances are all recovered, meaning that ingredients of bitter and rough tastes are also recovered in addition to eriocitrin. Consequently, the resulting material cannot be applied to drink and food products in view of the taste.
Therefore, an extract obtained by extracting a peel, a juice and a squeezed residue of citrus fruits containing eriocitrin with a polar solvent was applied to a synthetic adsorption resin to adsorb eriocitrin thereon, and it was recovered using hydrous ethanol. Then, it was found that a food material having a high concentration of eriocitrin could industrially be obtained at a low cost upon selectively removing ingredients of bitter and rough tastes. That is, it has been identified for the first time that an eluent (organic solvent) for recovering an adsorption product is selected and a specific organic solvent is used, whereby only eriocitrin can selectively be recovered, and that it can selectively be recovered industrially through quite a simple operation. As a result of further investigations based on these useful new findings, the invention has been finally completed.
The invention is described in detail below.
In practicing the invention, at least one of a peel and a squeezed juice residue which are secondary products provided after obtaining a juice and a squeezed juice of citrus fruits such as lemon, lime and the like is first extracted with a polar solvent.
Examples of the citrus fruits include lemon, lime, grapefruit, xe2x80x9cyuzuxe2x80x9d (Citrus junos), navel orange, Valencia orange, sour orange, xe2x80x9chassakuxe2x80x9d (Citrus hassaku), Satsuma mandarin, xe2x80x9ciyokanxe2x80x9d (Citrus iyo), xe2x80x9cdaidaixe2x80x9d (Citrus aurantium), Kabosu and Ponkan mandarin. These can be used singly or in combination. Lemon and lime are preferably used because these have a high concentration of eriocitrin.
The fruit juice thereof can be obtained by the Brown squeezing method or the FMC squeezing method. It is advisable that secondary products obtained by squeezing the fruit juice are used as a peel and a squeezed refuse. The peel and the squeezed refuse can be used as such. It is preferable that these are cut and pulverized.
The extraction is conducted at from room temperature to elevated temperatures (from 40 to 100xc2x0 C.) while being allowed to stand or stirred. It can also be conducted under increased pressure. In the extraction, water, alcohol, glycerol and glacial acetic acid are used as a polar solvent as required. These solvents may be used either singly or in combination. Further, water which is brought into direct contact with a peel, such as water used in feeding a fruit or a peel or washing water used in a squeezer may be utilized as an extract. That is, the feeding water and the washing water are satisfactorily contacted with a flesh, a peel and a squeezed residue, and eriocitrin has been already extracted therefrom. Accordingly, they are indeed polar solvent extracts of eriocitrin. Therefore, there is no need to extract the feeding water or the like with a polar solvent, and the subsequent treatment with the synthetic adsorption resin can immediately be conducted.
Then, pulps are removed through centrifugation or membrane separation, and the residue is applied to a synthetic adsorption resin to once adsorb eriocitrin and the like on the resin. As the synthetic adsorption resin, a styrene type and an acrylic type are common, and both are available. Examples thereof include DUOLITE S-861, DUOLITEES-865, AMBERLITEXAD-4, AMBERLITE XAD-7, AMBERLITE XAD-16 (products of Rohm and Haas Co.), DIAION HP 20 and SEPABEADS SP207 (products of Mitsubishi Chemical Industries Ltd.).
Further, high-speed centrifugation or flannel filtration is conducted before passing the extract through the synthetic adsorption resin to remove essential oil ingredients in the extract, making it possible to increase the amount of eriocitrin adsorbed on the resin and further to obtain a food material having a high concentration of eriocitrin efficiently. When the extract is treated with activated carbon instead of the treatment through the high-speed centrifugation or the flannel filtration, the bitter and rough tastes can be removed, and a food material having a high concentration of eriocitrin and having a less bitter taste can be obtained. However, there is also a demerit that the main ingredient is adsorbed on the activated carbon owing to the properties of the activated carbon to decrease the yield of eriocitrin.
After the extract is adsorbed on the resin, it is washed with water or hot water, and crude ingredients containing eriocitrin are eluted with an organic solvent. Then, the solvent is completely removed.
When the resin is washed with water, water of room temperature can be used. However, with the use of hot water of from 40xc2x0 C. to 100xc2x0 C., a food material containing eriocitrin and more free from bitter and rough tastes can be produced. Especially, with the use of hot water of from 60xc2x0 C. to 80xc2x0 C., a food material containing eriocitrin and all the more free from bitter and rough tastes can be produced. In view of the findings, namely, the property of the synthetic adsorption resin that the higher the temperature of washing water of the resin, the weaker the adsorption force on the resin and the property of the ingredient having the bitter taste that its adsorption force is weaker than that of eriocitrin, it has been clarified that the use of hot water of from 40xc2x0 C. to 100xc2x0 C. is preferable.
As the eluent used to recover eriocitrin adsorbed on the resin, an organic solvent is preferable, examples thereof being alcohol, acetone, hexane and chloroform. A polar solvent is especially preferable. Examples thereof include water, alcohol, glycerol and glacial acetic acid. These may be used either singly or in combination. With respect to the condition of the solvent used at this time, when the organic solvent is used as such, ingredients of bitter and rough tastes adsorbed on the resin along with eriocitrin, such as limonin, are also eluted. Therefore, when the solvent is used upon reducing the concentration thereof, the ingredients of bitter and rough tastes are adsorbed on the resin as such, and retained thereon, and eriocitrin alone is eluted selectively. The inventors have discovered this fact for the first time.
As the solvent, alcohol is preferably used. Ethanol is preferable because it is easy to use, and hydrous ethanol is especially preferable. The higher the alcohol content, the higher the eriocitrin content. Accordingly, with respect to the solvent condition, the alcohol content is preferably from 5% to less than 40%. When the ethanol content exceeds 40%, the material having a high concentration of eriocitrin is obtained, but a bitter taste is strong. Thus, a desired food material having a high concentration of eriocitrin with bitter and rough tastes reduced cannot be obtained. Thus, the content of less than 40% is preferable. Further, in order to obtain the desired product efficiently, it is advisable that the ethanol content is between 20 and 30%.
The solvent can be removed by a usual method such as concentration under reduced pressure as required.
The thus-obtained product having the high concentration of eriocitrin can be used, as such, as a food material. The form thereof is not limited to a liquid. It may be used in a food as a treated product such as a paste, a solid, a powder or a diluted product. Solidification and pulverization can be conducted through vacuum drying or freeze-drying as required.
The thus-obtained food material having the high concentration of eriocitrin can be utilized in beverages, foods and alcohols described below.
(1) Soft drinks black tea, barley water, green tea, oolong tea, blend tea, wild grass tea, herb tea, coffee, fruit juice, vegetable drink, cocoa, soybean milk, sports drink, carbonated drink, and milk drink
(2) Health foods vitamin drink, nutrient and nutrient aid food
(3) Other foods seasonings, vinegar, dressing, soup and xe2x80x9cfurikakexe2x80x9d (foods for sprinkling on cooked rice)
(4) Alcohols cocktail, xe2x80x9cchuhaixe2x80x9d (xe2x80x9cshochuxe2x80x9d (low-class distilled spirit) diluted with soda water), xe2x80x9csourxe2x80x9d (mixture of spirit, lemon juice, sugar, etc.), beer and wine
(5) Sweets candy., biscuit, caramel and snack sweet